In a major breakthrough for the future of global communications, a team of international researchers led by Japan’s National Institute of Information and Communications Technology (NICT) and Sumitomo Electric Industries has achieved the world’s fastest long-distance optical data transmission. The team successfully sent data at a rate of 1.02 petabits per second over a distance of 1,808 kilometres, using a specially designed 19-core optical fibre.
To put it into perspective, this distance is roughly equal to the journey from Sapporo to Fukuoka in Japan, from Missouri to Montana in the US, or from Berlin to Naples in Europe. The amount of data transmitted in just one second is more than what all internet users worldwide typically use in a day.
This remarkable achievement, presented at the 48th Optical Fiber Communication Conference (OFC 2025) in April, sets a new world record for both speed and distance using any kind of optical fibre. The capacity-distance product reached 1.86 exabits per second-kilometre, the highest ever recorded.
A new generation of optical fibre
What makes this achievement even more significant is that the 19-core fibre used in the test has the same outer diameter (0.125 mm) as standard single-core optical fibres currently in use. This means it can work with existing network infrastructure, making it easier to adopt for real-world use.
While earlier attempts have managed to reach over 1 petabit per second, those were limited to shorter distances (under 1,000 km). The team overcame this by designing a low-loss, wide-bandwidth 19-core fibre, allowing signals to travel much farther without quality loss. The optical fibre was manufactured by Sumitomo Electric, which also ensured that the fibre had low losses across the commonly used C and L wavelength bands.
Advanced transmission system
NICT and its partners developed a sophisticated system that could send and receive signals from all 19 cores at once. The setup included a transmitter, receiver, and 19 recirculating loops, each running through an 86.1 km fibre. The data passed through the loops 21 times, reaching a total distance of 1,808 km.
To maintain signal quality, the system used optical amplifiers, two per core, one for each band (C and L). In total, 180 wavelengths were used, each carrying data using a high-capacity format known as 16QAM (Quadrature Amplitude Modulation).
Meeting the world’s growing data needs
With the world’s data demand increasing rapidly due to services like video streaming, cloud computing, and 5G, this kind of breakthrough is essential. The team’s success shows that multi-core fibres, which allow multiple light signals to travel simultaneously, could be the key to building future high-capacity internet systems.
Previously, long-distance high-speed transmission was limited either by the number of cores or by signal loss over large distances. But this new development shows that with the right design and amplification systems, scalable and long-range high-speed networks are possible.
The work is part of a larger push by NICT and global researchers to explore new fibre types, such as multi-mode and coupled-core fibres, to break past current technological limits. While past experiments using these fibres showed promise, they were often limited by complex signal processing challenges. This latest result using coupled-core 19-core fibre over long distances is a strong step forward.
Looking ahead
This record-breaking experiment is more than just a technical victory, it represents a future where data can travel faster, farther, and more efficiently.
